Bailly J L, Borman A M, Peigue-Lafeuille H, Kean K M
Service de Bactériologie-Virologie, Faculté de Médecine, Clermont-Ferrand, France.
Virology. 1996 Jan 1;215(1):83-96. doi: 10.1006/viro.1996.0009.
The complete nucleotide sequence of the 5'-untranslated region (5'-UTR) of the genome of three ECHO virus type 25 strains (the JV4 reference strain and two wild isolates) was determined. The 5'-UTR of the two isolates shared 85 and 82% nucleotide identity with the reference strain. The overall folding of the predicted secondary structure of the ECHO virus 5'-UTRs showed significant conservation with that of the poliovirus. Most significant differences were observed in specific domains of the predicted IRES of the wild isolates. The efficiency with which ECHO virus type 25 5'-UTRs promoted internal initiation of translation was examined in an in vitro translation system. At low doses of input RNA, all three 5'-UTRs were similarly efficient in promoting internal ribosome entry and behaved similarly to the poliovirus IRES in that downstream cistron translation was markedly stimulated by the addition of HeLa cell extracts to standard reticulocyte lysates. At high RNA doses, the JV4 5'-UTR was much more efficient than the other two ECHO virus 5'-UTRs. This difference was much less marked when reticulocyte lysates were supplemented with 20% HeLa S-10 extracts, which suggests that the two less efficient 5'-UTRs were characterized by a reduced binding capacity to at least one factor present in HeLa cells. In MRC5 cell S-10 extract, internal initiation of translation was stimulated from the IRES of all three ECHO strains, the M1262 IRES being the least stimulated.
测定了3株25型埃可病毒（JV4参考毒株和2株野生分离株）基因组5′非翻译区（5′-UTR）的完整核苷酸序列。这2株分离株的5′-UTR与参考毒株的核苷酸同一性分别为85%和82%。埃可病毒5′-UTR预测二级结构的总体折叠与脊髓灰质炎病毒的显著保守。在野生分离株预测的内部核糖体进入位点（IRES）的特定结构域观察到最显著的差异。在体外翻译系统中检测了25型埃可病毒5′-UTR促进翻译内部起始的效率。在低剂量输入RNA时，所有3个5′-UTR在促进核糖体内部进入方面效率相似，并且在标准网织红细胞裂解物中添加HeLa细胞提取物时，下游顺反子翻译受到显著刺激，其行为与脊髓灰质炎病毒IRES相似。在高RNA剂量下，JV4 5′-UTR比其他两个埃可病毒5′-UTR效率高得多。当网织红细胞裂解物补充20%的HeLa S-10提取物时，这种差异不太明显，这表明两个效率较低的5′-UTR的特征是与HeLa细胞中至少一种因子的结合能力降低。在MRC5细胞S-10提取物中，所有3株埃可病毒的IRES均刺激了翻译的内部起始，其中M1262 IRES受到的刺激最小。
